Join::join() $columns parameter should not accept int.

[tyrsson]

phpdb/src/Sql/Join.php

Line 124 in 74363f4

array|int|string $columns = [Select::SQL_STAR],

I'm proposing narrowing this type to array|string especially in light of the fact that Select::join() only accepts array|string.

[simon-mundy]

Off the top of my head I can't even think where that would break anything... but I'll do some checking before I apply a fix.